LT-S-(L) Technical manual
hi-low voltage protector with ± 5% tolerance of normal voltage to ensure safe
operating of the compressor.
Unbalanced Voltage
Unbalanced voltage usually occurs because of variatio ns in the load.
During loading process, when one or more of the phases are different from the
other(s), unbalanced voltage will appear. This can be due to different
impedances, or type and value of the loading in each phase. Unbalanced
voltage can cause serious problems, particularly to the motor.
NEMA defines voltage unbalances as follows:
NEMA states that poly-phase motors shall operate successfully under
running conditions at rated load when voltage unbalance at the motor
terminals does not exceed 1%. Furthermore, operation of a motor with
over 5% unbalance is not recommended for it probably results in
motor damage.
Unbalanced voltages at motor terminals cause phase current unbalance
ranging from 6 to 10 times the percent of voltage unbalance for a fully loaded
motor. This causes motor over current resulting in excessive heat that shortens
motor life, and hence, eventual motor burnout. If the voltage unbalance is
great enough, the reduced torque capability might not be adequ ate for the
application and the motor will not attain rated speed.
6.1.3
MCC&LRA
Model
Start current LRA
（△
start/Y start
）
Max. operation current MCC（A）
LT-S-20/10
420/140
105
LT-S-30/12
620/206
160
LT-S-45/20
810/270
200
LT-S-55/25
875/292
240
LT-S-65/32
1430/477
285
LT-S-83/41
1430/477
360
